Method of arranging and brazing superposed commutator leads



Dec. 7, 1948. v c F. COBB EI'AL 2,455,560

METHOD 6F ARRANGING AND BRAZING SUPERPOSED COMMUTATOR LEADS Filed Aug.6, 1945 Ame/Mom 3pm 31. Emu/MW mlo/mag Patented Dec. 7, 1948 UNITEDSTATES PATENT OFFICE ration of Delaware Application August 6, 1945,Serial No. 609,186

7 Claims.

This invention relates in general to commutators and methods of makingthe same, and more Q I particularly to an arrangement of commutatorleads which permits brazing the leads in the slots of the commutatorbars without damaging the commutator insulation.

In dynamoelectric machines of the commutator type, each commutator baris generally connected to the armature winding through two leads orthrough two groups of parallel leads disposed one above the other inaxial alignment with the bar. The different pairs of leads are disposedsymmetrically around the armature shaft and, in general, the distancefrom the outer surface of the upper leads to the armature axis isgreater than the radius of the commutator cylindrical area engaged bythe brushes. Each commutator bar is therefore provided with a neck orriser of increased height which is slotted to receive the ends of theassociated leads. Both leads generally extend through the neck and reachthe step in the cylindrical outer surface of the commutator where bothare accessible for the application of heat for soldering or brazing themin the bar.

Sometimes, however, the lower lead is embedded in the commutator barbelow the level of the brush engaging area and is entirely inaccessible.Heat then can be transmitted to the lower lead only by conductionthrough the associated upper lead and through the adjacent portions ofthe commutator bar. Satisfactory soldering of the leads then requiresthe exercise of considerable care, and to braze the leads it isnecessary to heat the commutator neck for a considerable length of timeto temperatures far above the melting point of the brazing metal,thereby causing the commutator insulation to become damaged to an extentsuflicient to impair its effectiveness.

In making the latter type of commutator, itis therefore advantageous toprovide each lower lead with a bent end portion extending to thecylindrical outer surface of the commutator in axial alignment with theassociated upper lead so that both leads are accessible for directheating thereof. In addition, it is advantageous to provide the lowerlead or the upper lead or both leads with an extension protruding fromthe surface of the commutator, whereby additional heat supplied to theextension is conducted to the embedded part of the lead to acceleratethe fusion h of the brazing metal. Thisarrangement is particularlyconvenient when the lead ends are heated by induction, the protrudingextension then being inserted in the inductor coil serving to inducecurrents in the lead and in the adjacent portions of the commutator bar.

It is therefore an object of the present invention to provide animproved method of making a commutator to obtain that the lower andupper leads all reach the cylindrical outer surface of the commutator.

Another object of the present invention is to provide an improved methodof making a commutator having a cylindrical outer surface in such mannerthat the lead ends may be heated by induction for brazing thereof in theslots of the commutator bars.

Another object of the present invention is to provide a method ofbrazing commutator leads embedded adjacent the cylindrical outer surfaceof a commutator without damage to the commutator insulation.

Another object of the present invention is to provide a method ofbrazing commutator leads by supplying heat directly to the embedded partof the leads and to the adjacent portions of the commutator bar and alsosupplying heat indirectly thereto by conduction from a heated elementprotruding from the commutator surface.

Objects and advantages other than those above set forth will be apparentfrom the following description when read in connection with theaccompanying drawing, in which:

Fig. 1 is a view partly in elevation and partly in longitudinal crosssection of a commutator showing a pair of leads disposed for brazing inaccordance with the present invention;

Fig. 2 is a view partly in elevation and partly in cross section of oneembodiment of finished commutator bar with the two lead end portionsextending to a step of the commutator outer cylindrical surface;

Fig. 3 is a view partly inelev-ation and partly in cross section ofanother embodiment of finished commutator bar with the two lead endportions extending to different steps of the commutator outercylindrical surface; and

Fig. 4 is a view partly in elevation and partly in cross section of afurther embodiment of finished commutator bar having a stepless outerportion.

3 cylindrical surface to which the ends of the leads extend in axialalignment.

Referring more particularly to the drawing by characters of reference,Fig. 1 shows a commutator comprising a plurality of bars or segments 6,each bar being provided with the usual dovetail portion for holding thebars in a unitary assembly. The bars are mounted on a sleeve 1 to whichthey are fastened by means of a suitably shaped ring 8 backed by a nutii. The bars are insulated from the sleeve assembly by means of aninsulating tube II and of two pair of conical insulation rings l2, I3,E4, E5. The-different bars are insulated from each other by means oflaminated insulating segments I6. All the insulating materialincorporated in the commutator -may be of any known type used for thatpurpose and generally consists of mica splittings united by means of anorganic binder. The latter type of insulation is not seriously afiectedby momentary heating to the melting point of metals or alloys commonlyused in brazing operations but would be excessively damaged by heatingto substantially higher temperatures for a substantial length of time.

Fig. 1 shows the commutator disposed for brazinga pair'of'leads ll, I8to the slot l9 of-a commutator bar 25 shown in cross section. It will beobserved that the outer cylindrical surface 2! of the commutator isstepped, whereby commutator bar 20 is caused to present a neck portion22 wherein slot [9 is provided. As may beseen in the lower part of Fig.1 each slot has substantially the same width as the lead embeddedtherein, leaving only sufiicientclearance for the formation of a film ofbrazing metal between the leads and the walls of the slots. A sheet offlexible mica ll) insulates each upper lead from the adjacent lowerleads which are at different potentials.

The step of surface 2! is of--suchheightthat any portion of lower lead18 disposed below the embedded portion 23 of lead ll'is inaccessible forthe direct supply of heatthereto. Lead 28 is formed with intermediateportion 24 adapted to be embedded in slot l9 and a bent end For brazingleads 17,18 in slot E9 the intermediate portion 24 of lead 18 isembedded in the'bottom portion of slot 19 andportion "23 of'lead H isembedded in the portion of slot l9 extending between the portionMand'the surface 2 I. The end portion of lead i8 may be considered tocomprise a portion'25 directed perpendicularly to surface 2| andembedded in the portion of slot l9 adjacent surface2l, and a bend'26joining portions 24 and 25.

Prior to the brazing operatiomlead I8 may be cut flush with surface 2!.It is however more advantageous to provide-lead I8 with an extension '2?protruding from: slot l9 above surface 2|. The accessible surfaces'ofthe lead ends and the adjacent surfaces of bar 20 are coated with -,a:suitable .flux 28and a, rod of-brazing metalqZQ' is brought in contactwith :a convenient-point of the parts to be brazed. The brazingconnection may .be effected using a variety of known brazing metalcompositions, and in particular satisfactory results have beenconsistently obtained by using an alloy of 50% silver, 15 A copper, 16zinc and 18%cadmium with a flux havinga borax base with addition ofalkali bifluorides Orother halogen salts.

The lead portions .23, ,25, .2! .and the adjacent portions of neck-22may then .be-heated inany suitable known manner to bring them rapidly toa suitable watersupply pipe 32. When coil 3| has been properly disposedwith respect to the commutator either by moving the coil toward the:commutator or by moving the commutator toward the coil, the latter isconnected with a source ofalternating current 33 of any suitable typeconventionally represented on the drawing as asynchronousgenerator.

The current supplied to coil 3! is caused to be of such intensity,frequency and duration as to induce inthe superficial parts of leadportions 23, 25 and of the adjacent portions of neck 22 ourxrents-rwhichheat such parts rapidly to a substantially uniform temperature slightlyabove the fusion temperature of rod 29. Heat conducted from the heatedparts to the fluxand to rod2-9 causes the metal of the rodto melt and tounite leads 1'', I8 with neck 22. Additional current induced inprotruding lead-portion '27 likewise heats the latter and the heatproduced therein flows into the embedded part of lead l8 to acceleratethe fusion of the brazing metal and to assist'in maintaining the brazingmetal above its fusion temperature whileit is'flowing between the leadsand the walls of slot !9.

It will be understood that the intensity and duration of the flow ofcurrent through coil 3| and the location'of coil 3! will very with eachparticular arrangement of commutator leads and must be determinedexperimentally in every instance to insure that'the portions of-thecommutator bar adjacent toinsulation are not heated to such temperatureand for such Iengthcf-time as to cause the insulation to becomedamaged.For example, brazing of leads having across section-of A; inch by A inchmay be effected by the use of a 20 kilowattgenerator supplying 375kilocycle-current to the inductor during approximately 11 seconds. Toavoid overheating-of the insulation, it is generally advantageous'andfrequently essential to provide the commutator bar being brazed withartificial cooling means during the brazing operation.

As soon as the desired amount of melted brazing metal has run into slot19 to unite leads IT, IS with-neck 22,-the current in coil 3] isinterrupted and the coil is removed from engagement with extension 21.The difierent commutator bars are brazed one after the other in theabove described manner.

The induction-of heating current in extension 27 causes the flow ofheatingcurrent in the other portions of the "assembly-to be reduced toan extent which varies with the length of extension 21. The'latter'length should therefore be so selected that the heat which flowsfrom extension 2'! into the embedded portion of lead I8 during thebrazing operation isgreater than the decrease in heat generated in'theembedded-parts and the adjacent portions of the commutator bar.

Theabove describedprocedure may be varied to suit particulararrangements of leads. For instance coil 3! may first be disposed aboutthe end of extension 21 to preheat the extension without substantiallyraising the temperature of neck 22, the coil thereafter being disposedin close proximity to neck 22 as shown in "Fig. 1 to complete thebrazing operation. Depending on the dimensions of the parts to bebrazed, the entire brazing operation may even be performed with coil 3|inducing heating current substantially only in extension 21.

In some instances it may be preferable to omit extension 21 and toprovide instead an extension on upper lead l1. Both leads may also beprovided with such extensions, coil 3| then being increased in size tothe necessary extent to permit disposing the coil about the twoextensions.

When brazing of all the commutator bars is completed, the protrudingextensions may be left in place and may be twisted for assisting in ventilating the commutator. In general however the extensions are removedand the commutator is machined to its final dimensions. If the outersurface 2| of the commutator is stepped between the brush engaging areaand the bent portion of lead I8, each finished commutator bar has theoutline shown in Fig. 2. The commutator outer surface may also bestepped at the end. of lead I1, the finished commutator bar then havingthe outline shown in Fig. 3. The commutator outer sur face may also bemade stepless as shown in Fig. 4.

Although but a few embodiments of the present invention have been shownand described, it will be apparent to those skilled in the art thatvarious changes and modifications may be made therein without departingfrom the spirit of the invention or from the scope of the appendedclaims.

It is claimed and desired to secure by Letters Patent:

1. The method of making a commutator comprising the steps of providing alower lead with a bent end portion, embedding said lower lead in theslot of a commutator bar with said end portion extending at least to theouter surface of said commutator bar, embedding an upper lead endportion in the portion of said slot extending between said lower leadand said surface, applying flux and fusible metal to said lead endportions, and heating said lead end portions and the adjacent portionsof said commutator bar above the fusion temperature of said metal.

2. The method of making a commutator comprising the steps of providing alower lead with a bent end portion, embedding said lower lead in theslot of a commutator bar with said end portion extending at least to theouter surface of said commutator bar, embedding an upper lead endportion in the portion of said slot extending between said lower leadand said surface, applying flux and fusible metal to said lead endportions, and inducing in the superficial portions of said lead endportions and in the adjacent portions of said commutator bar electriccurrents heating said lead end portions and the adjacent portions ofsaid commutator bar to a substantially uniform temperature slightlyabove the fusion temperature of said metal.

3. The method of making a commutator comprising the steps of providing alower lead with a bent end portion, embedding an intermediate portion ofsaid lower lead in a portion of the slot of a commutator bar remote fromthe 00mmutator cylindrical outer surface with said bent end portionpartially protruding from said surface, embedding an upper lead endportion in the portion of said slot extending between said lower leadintermediate portion and said surface, applying flux and fusible metalto said lead end portions, supplying heat to the superficial portions ofthe embedded parts of said leads and of the adjacent part of saidcommutator bar to 6 cause fusion of said metal for uniting said lead endportions with said commutator bar, and supplying to said protrudinglower lead end por" tion additional heat flowing into the embedded partof said lower lead end portion to accelerate the fusion of said metal.

4. The method of making a commutator comprising the steps of providing alower lead with a bent end portion, embedding an intermediate portion ofsaid lower lead in a portion of the slot of a commutator bar remote fromthe commutator cylindrical outer surface with said bent end portionpartially protruding from said surface, embedding an upper lead endportion in the portion of said slot extending between said lower leadintermediate portion and said surface, applying flux and fusible metalto said lead end portions, inducing in the superficial portions saidlead end portions and in the adjacent portions of said commutator barelectric currents heating said lead end portions and the adjacentportions of said commutator bar to a substantially uniform temperatureslightly above the fusion temperature of said metal, and inducing insaid protruding lower lead end portion additional current supplyingadditional heat flowing into the embedded part of said lower lead endportion to accelerate the fusion of said metal.

5. The method of making a commutator comprising the steps of embedding alead structure in the slot of a. commutator baiadjacent an outer surfaceof the commutator, applying flux and fusible metal to said leadstructure, and inducing in the superficial portions of said leadstructure and of the adjacent portions of said commutator bar electriccurrents heating said lead structure and the adjacent portions of saidcommutator bar to a substantially uniform temperature slightly above thefusion temperature of said metal.

6. The method of making a commutator comprising the steps of embedding alead structure in the slot of a commutator bar adjacent an outer surfaceof the commutator, disposing an element of said lead structure toprotrude from said slot above the said surface, applying flux andfusible metal to said lead structure, inducing in the superficialportions of said lead structure and of the adjacent portions of saidcommutator bar electric currents heating said lead structure and theadjacent portions of said commutator bar to a substantially uniformtemperature slightly above the fusion temperature of said metal, andinducing in said protruding element additional current supplyingadditional heat flowing into the embedded part of said element toaccelerate the fusion of said metal.

7. The method of making a commutator comprising the steps of embedding alead structure in the slot of a commutator bar adjacent an outer surfaceof the commutator, disposing an element of said lead structure toprotrude from said slot above the said surface, applying flux andfusible metal to said lead structure, supplying heat to the superficialportions of the embedded part of said lead structure and of the adjacentparts of said commutator bar to cause fusion of said metal for unitingsaid lead structure with said commutator bar, and supplying to saidprotruding element additional heat fiowing into the embedded part ofsaid lead structure to accelerate the fusion of said metal.

CARROLL F. COBB. EDWARD F. BRILL. JOHN R. GUENTHER.

(References on following page) Number" Name Date- REFERENGES CITED2,351,021 Dick June13, 1944 The following references are of record inthe 2 57 111, Hemphjll 29 1944 fileof this paioent:v 2,379,145 GraybrookJune 26, 1945 UNITED STATESPATENTS- 5; 2,400,902 Allen May 1946 NumberName Date OTHER REFERENCES r -2 1911 Bulletin 12A (1943), Handy &Harman, New 1 3 MclvFlnn 3, 1941 York, New York, pages 3, 4 and 15-17(Copy in 2,251,326 Cullm Aug. 5,1941 Division 0

